1. Field of the Invention
The present invention relates to a susceptor and a manufacturing method thereof. More specifically, the present invention relates to a susceptor capable of reliably charging electricity to an inner electrode built in the susceptor, and a manufacturing method of the susceptor, which can manufacture the susceptor at high yield and at a low price.
2. Description of the Related Art
In a dry etching apparatus or a CVD apparatus used in the manufacturing process of semiconductors such as ICs, LSIs, or VLSIs, in order to evenly perform film formation by means of etching or CVD for each wafer, single wafer processing has been recently developed wherein a plate sample such as a semiconductor wafer, a liquid crystal substrate glass or a printed board is processed one by one. In this single wafer processing process, in order to hold the plate samples one at a time in a processing chamber, the plate sample is mounted on a sample stand (pedestal) referred to as a susceptor, and subjected to predetermined processing.
This susceptor must endure use in plasma, and also must endure use at high temperatures. Hence it is required to have excellent plasma resistance and large heat conductivity.
As such a susceptor, one consisting substantially of a ceramics sintered body with excellent plasma resistance and heat conductivity is used.
These susceptors include ones provided with an internal electrode such as an electrostatic chuck electrode for generating an electric charge thereinside for securing a plate sample with electrostatic attraction, a heater electrode for energizing with electricity and generating heat to heat the plate sample, or a plasma generating electrode for energizing with high-frequency power to generate plasma for plasma processing.
FIG. 3 shows one example of a susceptor having such an internal electrode built therein. The susceptor 15 comprises a placement plate 11 for placing a plate sample (not shown) thereon, a support plate 13 for supporting this placement plate 11, an internal electrode 12 clamped and held between this placement plate 11 and the support plate 13, and feeding terminals 14 inserted in the support plate 13 so as to come in contact with the internal electrode 12, for supplying electric current to the internal electrode 12.
As a manufacturing method of such susceptors 15, there can be mentioned, for example, a method wherein fixation holes 16 for connecting the feeding terminals 14 to the internal electrode 12 are formed beforehand in the support plate 13, feeding terminals 14 made of metal are mounted in these fixation holes 16, an internal electrode 12 comprising a refractory metal such as tungsten, tantalum or molybdenum is arranged between the support plate having these feeding terminals 14 and the placement plate 11, and these are bonded by various binders under application of pressure.
In the manufacturing method of such a susceptor 15, however, at the time of bonding the placement plate 11 and the support plate 13 having the feeding terminals 14, it is difficult to approximate the coefficient of thermal expansion of the placement plate 11 and the support plate 13 to that of the feeding terminals 14. Also, it is necessary to use a refractory metal such as tungsten, tantalum or molybdenum, which has a high heat resistance and is expensive, for the metal forming the feeding terminals 14.
Moreover, at the time of high-temperature bonding under application of pressure, since the Young""s modulus of the feeding terminals 14 made of metal and the Young""s modulus of the placement plate 11 and the support plate 13 are very different, if a large pressure is applied, these fracture due to a difference in the deformation modulus. Therefore, these cannot be pressed sufficiently, and the electrical connection between the feeding terminals 14 and the internal electrode 12 is thus not sufficient, or a gap occurs between the internal electrode 12 and the placement plate 11. As a result, depending on the application of the internal electrode 12, the electrostatic attractive force decreases, the heater heating performance decreases, or plasma is not generated on the placement plate 11. Furthermore, the binder is exposed so that the constituents thereof volatilize and disperse, thereby contaminating the plate sample.
Therefore, in order to solve these problems, as a method of forming an internal electrode 12 in the susceptor 15 there is generally adopted a manufacturing method wherein, for example, a conductive paste in which an electrode material serving as the internal electrode 12 dispersed in an organic solvent or the like is printed on a support plate 13 in a predetermined pattern, and after the support plate 13 and a placement plate 11 are overlapped on each other and sintered and integrally formed via a surface on which the conductive paste comprising the electrode material is printed, fixation holes 16 are bored in the support plate 13 so as to reach the internal electrode 12, in order to form a conductive circuit between the internal electrode 12 and the outside of the susceptor 15, metallic feeding terminals 14 are mounted in these holes, and the metallic feeding terminals 14 and the internal electrode 12 are bonded via a brazing filler metal.
As another conventional built-in electrode type susceptor, there can be mentioned a susceptor comprising; a placement plate 11 for placing a plate sample thereon, a support plate 13 for supporting this placement plate 11, a conductive binder layer serving as an internal electrode 12 and integrally bonding the placement plate 11 and the support plate 13, and feeding terminals 14 buried in the support plate 13 so as to come in contact with the conductive binder layer, for feeding electric current to the internal electrode 12. The placement plate 11 comprises a dielectric made of a nonconductive ceramics sintered body, the support plate 13 comprises a substrate made of a nonconductive ceramics sintered body, and the conductive bond layer is formed of organic matter or metal.
In this kind of built-in electrode type susceptor 15, however, as described above, since the placement plate 11 and the support plate 13 are bonded by the conductive binder layer comprising a different material, bonding between the placement plate 11 and the support plate 13 is insufficient. Hence, corrosive gas or plasma enters in from the boundary therebetween, so that there is a possibility that the internal electrode 12 may be exposed to the gas or plasma, or that the bonding interface between the placement plate 11 and the support plate 13 may be broken, thereby causing a problem in that the corrosion resistance and the plasma resistance of the susceptor 15 is not sufficient.
In order to solve these problems, in the conventional manufacturing method of susceptors 15, it is necessary to ensure the bonding between the placement plate 11 and the susceptor 13, so that any gas or plasma does not enter into the junction.
As means for solving these problems, for example as shown in FIG. 4 and FIG. 5, there has been considered a method in which the above described placement plate 21 is structured with a ring-shape flange 21a provided on the side margin thereof to thereby form a disc-like concave portion 21b, and a support plate 23 having a conductive bond layer serving as an internal electrode 22 and a feeding terminal 24 built therein, is assembled into the concave portion 21b of the placement plate 21. In this method, however, it is necessary to design the placement plate 21 in a shape having the above structure, and to design the conductive bond layer and the support plate 23 in a shape so as to fit into the concave portion 21b of the placement plate 21 without any gap. As a result, there is a problem in that the manufacturing process of the susceptor 25 becomes complicated.
As described above, in the manufacturing method of susceptors 25 in which after bonding the placement plate 21 and the support plate 23, the fixation hole is formed by boring, however, the boring operation for the hole for mounting the feeding terminals 24 is performed from the surface of the support plate 23, and the formation of the hole must be stopped accurately at the surface contacting with the internal electrode 22. Moreover, it is required that the internal electrode 22 and the feeding terminals 24 be satisfactorily brought into contact with each other and electrically bonded completely. When the hole does not reach the internal electrode 22, or when the internal electrode 22 has been penetrated through, the electrical bonding becomes imperfect, so that the internal electrode 22 is unreliably charged with electricity.
Moreover, the thickness of the internal electrode 22 is normally of an order of several tens of xcexcm. Therefore the boring operation becomes a very inefficient operation, since work must be performed at a boring speed less than an order of the thickness of the internal electrode 22. Also, since the stop position cannot be accurately determined, this also becomes a cause for a decrease in the work yield.
Furthermore, as in the case where the internal electrode 22 is a bipolar type electrostatic chuck electrode, in the case where the position of the feeding terminals 24 on the pattern plane of the internal electrode 22 is important, it is necessary to perform the boring operation carefully, while monitoring the boring position using an X-ray transmission apparatus or the like. Hence, the operation needs time and effort.
As described above, there is heretofore no adequate susceptor 25 having the internal electrode 22 and the feeding terminals 24 formed therein in an accurate position and capable of reliably energizing the internal electrode 22, nor an adequate susceptor manufacturing method capable of manufacturing such a susceptor 25 at high yield and at a low price.
In view of the above problems, it is a specific object of the present invention to provide susceptors capable of reliably energizing an internal electrode formed therein, and a susceptor manufacturing method which can provide a built-in electrode type susceptor having excellent corrosion resistance and plasma resistance, in which corrosive gas or plasma does not enter into the susceptor from the bonding surface between a placement plate and a support plate, as well as being capable of providing such a built-in electrode type susceptor easily, at high yield and at a low price.
The present inventors have conducted a keen study for solving the above problems, and have developed a method for obtaining a built-in electrode type susceptor by boring a fixation hole in a support plate, fitting a feeding terminal to the support plate having this fixation hole, and after forming a conductor serving as an internal electrode beforehand, overlapping this with a placement plate on the support plate and performing sintering and bonding to integrate these plates. At this time, by selecting and combining a specific material for each member of the placement plate, the support plate, the internal electrode and the feeding terminal, all the problems that the conventional susceptor has can be solved, and susceptors having excellent corrosion resistance and plasma resistance can be provided at a low price.
That is to say, the invention according to a first aspect is a built-in electrode type susceptor comprising a placement plate for placing a plate sample thereon, a support plate for supporting this placement plate, an internal electrode provided between these placement plate and support plate so as not to come in contact with the outside, and a feeding terminal provided penetrating through the support plate so as to come in contact with the internal electrode, wherein the placement plate and the support plate are integrally bonded by a nonconductive material having the same composition or the same main component as that of the material constituting these plates.
By making a susceptor having such a construction, there is an advantage in that susceptors excellent in corrosion resistance and plasma resistance can be obtained.
The invention according to a second aspect is a built-in electrode type susceptor comprising a placement plate for placing a plate sample thereon, a support plate for supporting this placement plate, an internal electrode provided between these placement plate and support plate so as not to come in contact with the outside, and a feeding terminal provided penetrating through the support plate so as to come in contact with the internal electrode, wherein the internal electrode and the feeding terminal are formed of a conductive ceramics.
By making a susceptor having such a construction, there is an advantage in that a choice of specific resistance is widened, and an internal electrode having optimum specific resistance can be easily obtained, depending on the function aimed at by the internal electrode.
The invention according to a third aspect is a built-in electrode type susceptor wherein the conductive ceramics is any one kind of composite ceramics conductors selected from an alumina-tantalum carbide composite ceramics conductor, an alumina-tungsten composite ceramics conductor, an alumina-silicon carbide composite ceramics conductor, an aluminum nitride-tungsten composite ceramics conductor, or an aluminum nitride-tantalum composite ceramics conductor.
By making a susceptor having such a construction, there is an advantage in that the specific resistance of the internal electrode can be chosen in a wide range of from 1xc3x9710xe2x88x925 to 1xc3x97105.
The invention according to a fourth aspect is a built-in electrode type susceptor, wherein the alumina-tantalum carbide composite ceramics conductor has a material containing tantalum in an amount of from 54 to 71% by weight.
The invention according to a fifth aspect is a built-in electrode type susceptor, wherein the alumina-tungsten composite ceramics conductor has a material containing tungsten in an amount of from 54 to 95% by weight.
The invention according to a sixth aspect is a built-in electrode type susceptor, wherein the alumina-silicon carbide composite ceramics conductor has a material containing silicon carbide in an amount of from 5 to 30% by weight.
By using the composite ceramics conductor of such a material, it becomes possible to obtain an internal electrode and a feeding terminal having an adequate specific resistance and adequate coefficient of thermal expansion and Young""s modulus. As a result, there is an advantage in that the occurrence of a thermal stress fracture can be suppressed to increase the product yield, and the product can be provided at a low price.
The invention according to a seventh aspect is a built-in electrode type susceptor, wherein the placement plate and the support plate comprise an alumina group sintered body or an aluminum nitride sintered body.
By making a susceptor having such a construction, there is an advantage in that susceptors strong against a thermal shock and excellent in corrosion resistance and plasma resistance can be obtained.
The invention according to an eighth aspect relates to a susceptor manufacturing method comprising steps of: preparing a plate-like placement plate and support plate from a ceramics sintered body; forming a fixation hole for fixing a feeding terminal in the support plate; fitting the feeding terminal in the fixation hole so as to penetrate through the support plate; forming a conductive material layer serving as an internal electrode on the support plate holding the feeding terminal, so as to come in contact with the feeding terminal; overlapping the support plate and the placement plate on each other via the conductive material layer, and subjecting these to sintering processing under application of pressure to thereby integrate these plates; and forming an internal electrode consisting of the conductive material layer between these support plate and placement plate.
By having a susceptor manufacturing method involving such steps, there is the advantage that susceptors can be provided at a low price by a simple method.
The invention according to a ninth aspect is a susceptor manufacturing method, wherein when the support plate and the placement plate are overlapped on each other, a nonconductive material layer comprising a powdery material having the same composition or the same main component as that of the ceramics sintered body constituting the placement plate and the support plate, is formed in an area other than the area where the conductive material layer is formed on the support plate.
By having a susceptor manufacturing method involving such steps, since the nonconductive material layer is provided in the interface between the placement plate and the support plate to integrally bond these plates, there is an advantage in that susceptors excellent in the corrosion resistance and the plasma resistance can be easily obtained. Moreover, the surface shape of the placement plate and the support plate is not required to be machined to a complicated shape, and need only be made to a simple plate form. As a result, it becomes possible to provide susceptors at high yield and at a low price.
The invention according to a tenth aspect is a susceptor manufacturing method, wherein as the conductive material serving as the internal electrode or the feeding terminal, any one kind selected from an alumina-tantalum carbide composite ceramics conductive material, an alumina-tungsten composite ceramics conductive material, an alumina-silicon carbide composite ceramics conductive material, an aluminum nitride-tungsten composite ceramics conductive material, an aluminum nitride-tantalum composite ceramics conductive material, or a high melting metal is used.
By having a susceptor manufacturing method involving such steps, there is an advantage in that materials having adequate specific resistance can be selected and combined.